Acceleration control device for a hydraulic drive unit

Abstract

An acceleration control device for a hydraulic drive unit having a rotatable control shaft movable between an on position and an off position. An arm is connected to the control shaft for rotating the shaft between the off and on positions. A motive apparatus is movable between a first position which corresponds to the off position of the control shaft and a second position which corresponds to the on position of the control shaft. A mechanical linkage is connected between the motive apparatus and the arm. The linkage imparts movement to the arm in response to movement of the motive apparatus to cause the control shaft to move between the off and on positions as the motive apparatus moves between the first and second positions, respectively. The linkage is configured to provide a substantially nonlinear relationship between the speed of the arm and the speed of the motive apparatus. The linkage is further configured so that the speed of the arm is at a minimum in relation to the speed of the motive apparatus when the control shaft is immediately adjacent its off position. The speed of the arm increases in relation to the speed of the motive means as the control shaft is moved away from its off position.

I claim: 
     
       1. An acceleration control device for a material transfer apparatus such as a conveyor or the like, comprising: a hydraulic drive unit for imparting motion to the material transfer apparatus, said drive unit having a hydraulic fluid pump that provides power for moving the material transfer apparatus, the fluid output of said pump and thus the speed of the material transfer apparatus being determined by the position of a rotatable control shaft about its longitudinal axis between an off position corresponding to a low fluid output configuration of the pump and a stopped condition of the material transfer apparatus, and an on position corresponding to a high fluid output configuration of the pump and a moving condition of the material transfer apparatus, the change in the fluid output of the pump caused by rotation of said control shaft to positions between said off and on positions and thus the acceleration or deceleration of the material transfer apparatus being proportional to an arc length through which said control shaft is rotated;   crank means connected to said control shaft for rotating said control shaft about its longitudinal axis between said off and on positions in response to rotation of said crank means about the longitudinal axis of said control shaft, the arc length through which said control shaft is rotated being proportional to the arc length through which said crank means is rotated;   support means;   motive means supported on said support means, said motive means having a movable element and being configured to move said element through a distance between a first position which corresponds to the off position of said control shaft and a second position which corresponds to the on position of said control shaft;   actuation means for actuating said motive means to move said element between said first and second positions;   a mechanical linkage connected between said movable element of said motive means and said crank means to impart rotational movement to said crank means in response to movement of said element, said linkage being configured together with said crank means so that movement of said element between its first and second positions causing rotational movement of said crank means causes said control shaft to be rotated between its off and on positions, respectively; and   said mechanical linkage being further configured to provide a substantially nonlinear relationship between the distance through which said movable element is moved by said motive means and the arc length through which said crank means is rotated by said movable element over a given time interval such that the arc length through which said crank means is rotated is at a minimum in relation to the distance through which said movable element is moved when said element is immediately adjacent its first position and the arc length through which said crank means is rotated increases gradually in relation to the distance through which said movable element is moved as said element is moved away from its first position, whereby said nonlinear relationship is also established between said movable element and said control shaft so that moving said movable element through said distance causes said control shaft and thus the material transfer apparatus to accelerate and decelerate gradually to minimize disturbances of the conveyed material associated with starting and stopping movements.   
     
     
       2. The device of claim 1, wherein said mechanical linkage is connected between said movable element and said support means and is configured to move said crank means in the direction of said support means in response to movement of said element from said first to said second positions. 
     
     
       3. The device of claim 1, wherein said movable element moves away from said first position in an initial direction of movement and said mechanical linkage is oriented generally perpendicular to the initial direction of movement of said movable element when said movable element is in said first position. 
     
     
       4. The device of claim 1, wherein said motive means comprises a pneumatic cylinder and said movable element comprises a rod reciprocally supported in said cylinder and pivotally connected to said mechanical linkage. 
     
     
       5. The device of claim 1, wherein said mechanical linkage comprises first and second elongate links, each of said links having an inboard and an outboard end and being pivotally interconnected at their inboard ends at a pivot point and pivotally connected at their outboard ends to said crank means and said support means, respectively, and said motive means comprises a cylinder having a base end and being pivotally connected at its base end to said support means, said movable element including a rod having an outboard end and being reciprocally supported in said cylinder and pivotally connected at its outboard end to said pivot point at the interconnection between said first and second links. 
     
     
       6. The device of claim 5, wherein said rod moves from said first position in an initial direction of movement and said first and second links are oriented generally perpendicular to the initial direction of movement of the rod when said rod is in said first position. 
     
     
       7. The device of claim 1, wherein said mechanical linkage comprises first and second elongate links pivotally interconnected at one of their ends at a pivot point and pivotally connected at their other ends to said crank means and said support means, respectively, and said movable element moves away from said first position in an initial direction of movement and said first and second links are oriented generally perpendicular to the initial direction of movement of said movable element when said movable element is in said first position. 
     
     
       8. The device of claim 1, wherein said support means is stationary in relation to the control shaft. 
     
     
       9. The device of claim 1, further comprising stop means for stopping movement of said crank means at the on and off positions of the control shaft. 
     
     
       10. An acceleration control device for a material transfer apparatus such as a conveyor or the like comprising: a hydraulic drive unit for imparting motion to the material transfer apparatus, said drive unit having a hydraulic fluid pump that provides power for moving the material transfer apparatus, the fluid output of said pump and thus the speed of the material transfer apparatus being determined by the position of a rotatable control shaft about its longitudinal axis between an off position corresponding to a low fluid output configuration of the pump and a stopped condition of the material transfer apparatus, and an on position corresponding to a high fluid output configuration of the pump and a moving condition of the material transfer apparatus, the change in the fluid output of the pump caused by rotation of said control shaft to positions between said off and on positions and thus the acceleration or deceleration of the material transfer apparatus being proportional to an arc length through which said control shaft is rotated;   an arm fixedly connected to said control shaft for rotating said control shaft about its longitudinal axis between said on and off positions in response to rotation of said arm about the longitudinal axis of said control shaft, the arc length through which said control shaft is rotated being directly proportional to the arc length through which said arm is rotated;   support means, said support means being stationary with respect to said arm and said control shaft;   cylinder means pivotally connected to said support means, said cylinder means including a rod reciprocally supported in said cylinder means, and being actuable to move said rod through a distance between a first position corresponding to the off position of said control shaft and a second position corresponding to the on position of said control shaft, said rod moving in an initial direction from said first position;   actuation means for actuating said cylinder means to move said rod between said first and second positions;   first and second elongate links pivotally interconnected at one of their ends at a pivot point and pivotally connected at their other ends to said arm and said support means, respectively;   said rod of said cylinder means being pivotally connected to said pivot point interconnecting said first and   said first and second links being oriented generally perpendicular to the initial direction of movement of said rod of said cylinder means when said rod is in said first position, where by moving said rod through said distance causes said control shaft and thus the material transfer apparatus to accelerate and decelerate gradually to minimize disturbances of the conveyed material associated with stopping and starting movements.   
     
     
       11. The device of claim 10, wherein said first and second links have substantially equal lengths.